Methyl methacrylate (MMA), which is representative of alkyl methacrylates, can be prepared in a reaction sequence starting with acetone cyanohydrin. In this process acetone cyanohydrin (ACN) is treated with sulfuric acid to form 2-hydroxy-2-methylpropionamide (HiBAm) and its sulfate ester (HiBAm.SE). These two compounds are then subjected to heat to form methacrylamide (MAAm). The MAAm is then treated with methyl alcohol and water to form methyl methacrylate (MMA). This reaction sequence is depicted as follows: ##STR1##
Because HiBAm reacts more slowly than HiBAm.SE to form MAAm the reaction time in the heat step must be extended and/or the temperature raised to reduce unreacted HiBAm. But there are limits to extending these parameters and not all the HiBAm is reacted, thus HiBAm is present when the MAAm is treated with CH.sub.3 OH and H.sub.2 O. The HiBAm present also reacts with the CH.sub.3 OH and H.sub.2 O, to form methyl 2-hydroxy-2-methyl propionate (MHiB). This reaction is depicted as follows: ##STR2##
The presence of the HiBAm reduces yield of MMA for several reasons. First, it is material that could have been converted to MAAm but wasn't; thus, less MAAm is present for conversion to MMA. Second, as HiBAm is heated longer or at a higher temperature to increase yield of MAAm, the heat begins to decompose the MAAm; thus reducing the amount of MAAm available for conversion to MMA.
It would be advantageous to find some means of preventing or reducing yield loss caused by presence of the HiBAm in the esterification step.